Temperature Conversions & Temperature Scales:

Celsius (Centigrade) and
FahrenheitConverting F-to-C, C-to-F

But if you want to UNDERSTAND the two scales,
and two ways to convert from F to C, and C to F, by
using a mathematical equation or visualizing-and-memory.

A convenient starting
point for conversions is to
compare the boiling and freezing points of water:

BOILING POINT of water is

100° C

212° F

difference in degrees =

100 C°

180 F°

FREEZING POINT of water is

0° C

32° F

As you can see by comparing numbers in the table above,
degrees differ in SIZE: 100 C° = 180 F°, so 5
C° = 9 F°
(a Celsius-degree is larger than a Fahrenheit-degree, andthere are 100 C-degrees between freezing and boiling, sothe Celsius scale originally was called the Centigrade scale)

The two scales also differ in STARTING POINTS: I find it useful to
think in terms of the freezing point of water, at 0° C = 32°
F .

Visualize-and-Memorize to convert between Celsius and Fahrenheit:
You can use the formulas above to convert by math-calculating, but for practical everyday conversions
I think it's more useful to memorize temperatures at intervals of 5° C and 9° F, as shown below where
(to understand-and-remember more easily) you can begin at 0/32 and move upward or downward:

°C

°F

etc

etc

40

104

35

95

30

86

25

77

20

68

15

59

10

50

5

41

0

32

- 5

23

-10

14

-15

5

-20

- 4

-25

-13

-30

-22

-35

-31

-40

-40

etc

etc

As shown by "etc" at the top and bottom, this 5-and-9 pattern
continues above and below the temperature range in the table.

To interpolate between these 5-and-9 temperatures, you canestimate that temperature changes by 1 C° for every 2 F°.And for more precision, use the easy calculations below;to make the math more intuitive and easy to remember,we'll start at 10-and-50 where both temps end in a "0":

°C

°F

°F

°F

°C

10

50 + 0/5

50.00

50

10

11

50 + 9/5

51.80

52

11

12

50 + 18/5

53.60

54

12

13

50 + 27/5

55.40

55

13

14

50 + 36/5

57.20

57

14

15

50 + 45/5

59.00

59

15

When rounded to the nearest degree, notice that
each interval (except the middle) is 2, for 22122.

10

11

12

13

14

15

50

52

54

55

57

59

+2

+2

+1

+2

+2

the differences are 2 2 1 2 2

Or, to estimate temperatures in the reverse direction, noticethe pattern of paired temperatures ( 1011-11 12-12 13-13 14-1415) for all of thein-between Celsius temperatures, but not for temperatures that are multiples of 5, such as 10 and 15.